WELL BENCHMARK Russian patent published in 2011 - IPC E21C39/00 

FIELD: mining.

SUBSTANCE: spacer unit is arranged as a hollow cylinder with stem rigidly fixed inside. Wedging elements are arranged in the form of elastic tabs from rubber, resin or polymers installed symmetrically in grooves at outer side of the spacer unit. Quantity of spacer units is accepted as equal to number of layers crossed by well, but not less than three. Number of elastic tabs is accepted as more than 3. At that the outer diametre of spacer unit is accepted as equal to 0.9 D with cylinder length of at least 3 D, and tab thickness d is accepted as more than 0.1 D.

EFFECT: higher force of well benchmark fixation and higher efficiency of its fixation.

3 dwg